class ShaderProgram {

    constructor(holder, options = {}) {

      options = Object.assign({
        antialias: false,
        depthTest: false,
        mousemove: false,
        autosize: true,
        side: 'front',
        vertex: `
            precision highp float;
    
            attribute vec4 a_position;
            attribute vec4 a_color;
    
            uniform float u_time;
            uniform vec2 u_resolution;
            uniform vec2 u_mousemove;
            uniform mat4 u_projection;
    
            varying vec4 v_color;
    
            void main() {
    
              gl_Position = u_projection * a_position;
              gl_PointSize = (10.0 / gl_Position.w) * 100.0;
    
              v_color = a_color;
    
            }`,
        fragment: `
            precision highp float;
    
            uniform sampler2D u_texture;
            uniform int u_hasTexture;
    
            varying vec4 v_color;
    
            void main() {
    
              if ( u_hasTexture == 1 ) {
    
                gl_FragColor = v_color * texture2D(u_texture, gl_PointCoord);
    
              } else {
    
                gl_FragColor = v_color;
    
              }
    
            }`,
        uniforms: {},
        buffers: {},
        camera: {},
        texture: null,
        onUpdate: (() => { }),
        onResize: (() => { }),
      }, options)

      const uniforms = Object.assign({
        time: { type: 'float', value: 0 },
        hasTexture: { type: 'int', value: 0 },
        resolution: { type: 'vec2', value: [0, 0] },
        mousemove: { type: 'vec2', value: [0, 0] },
        projection: { type: 'mat4', value: [1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1] },
      }, options.uniforms)

      const buffers = Object.assign({
        position: { size: 3, data: [] },
        color: { size: 4, data: [] },
      }, options.buffers)

      const camera = Object.assign({
        fov: 60,
        near: 1,
        far: 10000,
        aspect: 1,
        z: 100,
        perspective: true,
      }, options.camera)

      const canvas = document.createElement('canvas')
      const gl = canvas.getContext('webgl', { antialias: options.antialias })

      if (!gl) return false

      this.count = 0
      this.gl = gl
      this.canvas = canvas
      this.camera = camera
      this.holder = holder
      this.onUpdate = options.onUpdate
      this.onResize = options.onResize
      this.data = {}

      holder.appendChild(canvas)

      this.createProgram(options.vertex, options.fragment)

      this.createBuffers(buffers)
      this.createUniforms(uniforms)

      this.updateBuffers()
      this.updateUniforms()

      this.createTexture(options.texture)

      gl.enable(gl.BLEND)
      gl.enable(gl.CULL_FACE)
      gl.blendFunc(gl.SRC_ALPHA, gl.ONE)
      gl[options.depthTest ? 'enable' : 'disable'](gl.DEPTH_TEST)

      if (options.autosize)
        window.addEventListener('resize', e => this.resize(e), false)
      if (options.mousemove)
        window.addEventListener('mousemove', e => this.mousemove(e), false)

      this.resize()

      this.update = this.update.bind(this)
      this.time = { start: performance.now(), old: performance.now() }
      this.update()

    }

    mousemove(e) {

      let x = e.pageX / this.width * 2 - 1
      let y = e.pageY / this.height * 2 - 1

      this.uniforms.mousemove = [x, y]

    }

    resize(e) {

      const holder = this.holder
      const canvas = this.canvas
      const gl = this.gl

      const width = this.width = holder.offsetWidth
      const height = this.height = document.getElementById("header_wrap").offsetHeight
      const aspect = this.aspect = width / height
      const dpi = this.dpi = devicePixelRatio

      canvas.width = width * dpi
      canvas.height = height * dpi
      canvas.style.width = width + 'px'
      canvas.style.height = height + 'px'

      gl.viewport(0, 0, width * dpi, height * dpi)
      gl.clearColor(0, 0, 0, 0)

      this.uniforms.resolution = [width, height]
      this.uniforms.projection = this.setProjection(aspect)

      this.onResize(width, height, dpi)

    }

    setProjection(aspect) {

      const camera = this.camera

      if (camera.perspective) {

        camera.aspect = aspect

        const fovRad = camera.fov * (Math.PI / 180)
        const f = Math.tan(Math.PI * 0.5 - 0.5 * fovRad)
        const rangeInv = 1.0 / (camera.near - camera.far)

        const matrix = [
          f / camera.aspect, 0, 0, 0,
          0, f, 0, 0,
          0, 0, (camera.near + camera.far) * rangeInv, -1,
          0, 0, camera.near * camera.far * rangeInv * 2, 0
        ]

        matrix[14] += camera.z
        matrix[15] += camera.z

        return matrix

      } else {

        return [
          2 / this.width, 0, 0, 0,
          0, -2 / this.height, 0, 0,
          0, 0, 1, 0,
          -1, 1, 0, 1,
        ]

      }

    }

    createShader(type, source) {

      const gl = this.gl
      const shader = gl.createShader(type)

      gl.shaderSource(shader, source)
      gl.compileShader(shader)

      if (gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {

        return shader

      } else {

        console.log(gl.getShaderInfoLog(shader))
        gl.deleteShader(shader)

      }

    }

    createProgram(vertex, fragment) {

      const gl = this.gl

      const vertexShader = this.createShader(gl.VERTEX_SHADER, vertex)
      const fragmentShader = this.createShader(gl.FRAGMENT_SHADER, fragment)

      const program = gl.createProgram()

      gl.attachShader(program, vertexShader)
      gl.attachShader(program, fragmentShader)
      gl.linkProgram(program)

      if (gl.getProgramParameter(program, gl.LINK_STATUS)) {

        gl.useProgram(program)
        this.program = program

      } else {

        console.log(gl.getProgramInfoLog(program))
        gl.deleteProgram(program)

      }

    }

    createUniforms(data) {

      const gl = this.gl
      const uniforms = this.data.uniforms = data
      const values = this.uniforms = {}

      Object.keys(uniforms).forEach(name => {

        const uniform = uniforms[name]

        uniform.location = gl.getUniformLocation(this.program, 'u_' + name)

        Object.defineProperty(values, name, {
          set: value => {

            uniforms[name].value = value
            this.setUniform(name, value)

          },
          get: () => uniforms[name].value
        })

      })

    }

    setUniform(name, value) {

      const gl = this.gl
      const uniform = this.data.uniforms[name]

      uniform.value = value

      switch (uniform.type) {
        case 'int': {
          gl.uniform1i(uniform.location, value)
          break
        }
        case 'float': {
          gl.uniform1f(uniform.location, value)
          break
        }
        case 'vec2': {
          gl.uniform2f(uniform.location, ...value)
          break
        }
        case 'vec3': {
          gl.uniform3f(uniform.location, ...value)
          break
        }
        case 'vec4': {
          gl.uniform4f(uniform.location, ...value)
          break
        }
        case 'mat2': {
          gl.uniformMatrix2fv(uniform.location, false, value)
          break
        }
        case 'mat3': {
          gl.uniformMatrix3fv(uniform.location, false, value)
          break
        }
        case 'mat4': {
          gl.uniformMatrix4fv(uniform.location, false, value)
          break
        }
      }

      // ivec2       : uniform2i,
      // ivec3       : uniform3i,
      // ivec4       : uniform4i,
      // sampler2D   : uniform1i,
      // samplerCube : uniform1i,
      // bool        : uniform1i,
      // bvec2       : uniform2i,
      // bvec3       : uniform3i,
      // bvec4       : uniform4i,

    }

    updateUniforms() {

      const gl = this.gl
      const uniforms = this.data.uniforms

      Object.keys(uniforms).forEach(name => {

        const uniform = uniforms[name]

        this.uniforms[name] = uniform.value

      })

    }

    createBuffers(data) {

      const gl = this.gl
      const buffers = this.data.buffers = data
      const values = this.buffers = {}

      Object.keys(buffers).forEach(name => {

        const buffer = buffers[name]

        buffer.buffer = this.createBuffer('a_' + name, buffer.size)

        Object.defineProperty(values, name, {
          set: data => {

            buffers[name].data = data
            this.setBuffer(name, data)

            if (name == 'position')
              this.count = buffers.position.data.length / 3

          },
          get: () => buffers[name].data
        })

      })

    }

    createBuffer(name, size) {

      const gl = this.gl
      const program = this.program

      const index = gl.getAttribLocation(program, name)
      const buffer = gl.createBuffer()

      gl.bindBuffer(gl.ARRAY_BUFFER, buffer)
      gl.enableVertexAttribArray(index)
      gl.vertexAttribPointer(index, size, gl.FLOAT, false, 0, 0)

      return buffer

    }

    setBuffer(name, data) {

      const gl = this.gl
      const buffers = this.data.buffers

      if (name == null && !gl.bindBuffer(gl.ARRAY_BUFFER, null)) return

      gl.bindBuffer(gl.ARRAY_BUFFER, buffers[name].buffer)
      gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(data), gl.STATIC_DRAW)

    }

    updateBuffers() {

      const gl = this.gl
      const buffers = this.buffers

      Object.keys(buffers).forEach(name =>
        buffers[name] = buffer.data
      )

      this.setBuffer(null)

    }

    createTexture(src) {

      const gl = this.gl
      const texture = gl.createTexture()

      gl.bindTexture(gl.TEXTURE_2D, texture)
      gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, 1, 1, 0, gl.RGBA, gl.UNSIGNED_BYTE, new Uint8Array([0, 0, 0, 0]))

      this.texture = texture

      if (src) {

        this.uniforms.hasTexture = 1
        this.loadTexture(src)

      }

    }

    loadTexture(src) {

      const gl = this.gl
      const texture = this.texture

      const textureImage = new Image()

      textureImage.onload = () => {

        gl.bindTexture(gl.TEXTURE_2D, texture)

        gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, textureImage)

        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR)
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR)

        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE)
        gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE)

        // gl.generateMipmap( gl.TEXTURE_2D )

      }

      textureImage.src = src

    }

    update() {

      const gl = this.gl

      const now = performance.now()
      const elapsed = (now - this.time.start) / 5000
      const delta = now - this.time.old
      this.time.old = now

      this.uniforms.time = elapsed

      if (this.count > 0) {
        gl.clear(gl.COLORBUFFERBIT)
        gl.drawArrays(gl.POINTS, 0, this.count)
      }

      this.onUpdate(delta)

      requestAnimationFrame(this.update)

    }

  }

  const pointSize = 3.8

  const waves = new ShaderProgram(document.querySelector('.waves'), {
    texture: '',
    uniforms: {
      size: { type: 'float', value: pointSize },
      field: { type: 'vec3', value: [0, 0, 0] },
      speed: { type: 'float', value: 8 },
    },
    vertex: `
        #define M_PI 3.1415926535897932384626433832795
    
        precision highp float;
    
        attribute vec4 a_position;
        attribute vec4 a_color;
    
        uniform float u_time;
        uniform float u_size;
        uniform float u_speed;
        uniform vec3 u_field;
        uniform mat4 u_projection;
    
        varying vec4 v_color;
    
        void main() {
    
          vec3 pos = a_position.xyz;
    
          pos.y += (
            cos(pos.x / u_field.x * M_PI * 8.0 + u_time * u_speed) +
            sin(pos.z / u_field.z * M_PI * 8.0 + u_time * u_speed)
          ) * u_field.y;
    
          gl_Position = u_projection * vec4( pos.xyz, a_position.w );
          gl_PointSize = ( u_size / gl_Position.w ) * 100.0;
    
          v_color = a_color;
    
        }`,
    fragment: `
        precision highp float;
    
        uniform sampler2D u_texture;
    
        varying vec4 v_color;
    
        void main() {
    
          gl_FragColor = v_color * texture2D(u_texture, gl_PointCoord);
    
        }`,
    onResize(w, h, dpi) {

      const position = [], color = []

      const width = 400 * (w / h)
      const depth = 800
      const height = 4
      const distance = 6

      for (let x = 0; x < width; x += distance) {
        for (let z = 0; z < depth; z += distance) {

          position.push(- width / 2 + x, -30, -depth / 2 + z)
          color.push(0, 1 - (x / width) * 1, 0.5 + x / width * 0.5, z / depth)

        }
      }

      this.uniforms.field = [width, height, depth]

      this.buffers.position = position
      this.buffers.color = color

      this.uniforms.size = (h / 400) * pointSize * dpi

    },
  })